Method of making a paving material



Patented Dec. 7, 1937 t i V 1 AUNIT ED" STATES PATENT ow g;-

Drawing. Application August..26,.1935',,

Serial No. 37,981 r 3 Claims. (Cl. 106 -31) This inventionrelates to a. compositionsuit- The object of. the invention is tov obtain. a able for the construction of pavements, walks, greatly." improved. compositionutilizing the nattennis courts and the. like and particularly to ural .maltharcontained-in sandstone rock asphalt improved asphalt concrete.- and methods of makof Kentucky but. preferably limestone rock such 5 ing the same The composition. and: method of. as that found in' southern Ohio in Highland 5.

the present invention are improvements over the j County, which is almost identical with the maltha. composition and. method-disclosed in. my prior found: in. Kentucky sand rock and similar impatent for Asphaltic concrete paving, No. pregnated rock. In.v this. rock the maltha is held 1,757,661, granted May 6,1930. l n 3 V in minute globules which are apparently con- As pointed out in said patent;v improved asnectedtogether; It is: therefore only necessary phalt concrete. suitable for. pavements: is obin. carrying out the. present: process to crush the tained by combining natural maltha contained maltha. containing. rock to pass the inch. inrock. asphalt. with asphaltic cement thereby screen and be retainedron a. inch screen so producing a bituminous mat'erialthat is more ad that; the limestone itself maybe utilized as the 16' hesive, more ductile and self-healing. than the. aggregate in, the composition. The maltha imusualubituminous binder obtained from blown pregnated limestone may be. crushed to sand oils or even natural: asphalt materials on. acsize if. desired but in that. case, the usual. trap count of high percentage..oihydrocarbons of the rock or other coarse. aggregate must be added. malthene group incorporated in. the improved. If: the crushed rockis immersed in naptha 20 binder. orother' hydrocarbon solvent or distillate at or- 20 I have found. that the addition of maltha dinary room temperature for one; minute, apsuch as found in sand rock in Kentucky and proximately. one-half of the maltha content will limestone. rock in Ohio toasphaltic cement or be extracted. If. the rock is crushed to sand asphalt: pitch; in a ratio. of 1:4 provides maxi.- passing .a 30 mesh screen, approximately 100 mum cementing value, adhesiveness, ductility and percent of the maltha is extracted in the same 25 other desirable properties sought in paving. matime. 1 terials regardless of the method by which'the By experiment I have; found that I can succombination is=effectediprovided that. the method. cessfully combine a large proportion of. the maldoes not require.excessiveheating with.v resultant tha in the crushed limestone rock with asphaltic '30 cracking of the maltha. which converts thesame. cement, while cold, by adding asphaltic cement into hard brittle compounds of little or no value made'liquid by the addition of solvent such as as-ai binder. The'proportions of maltha to cenaptha',..the;ratio of the extracted maltha to ment may vary between 1:3 to 1:5 by weight the asphaltic cement being preferably 1:4. with satisfactory results. This discovery is the In practicethe best results are obtained by basis of my'co-pending application, SerialNumusing thinned asphalt or asphalt cut back con 35 her 755,832 for Asphalt paving composition and sisting of asphalt cement of the desired penemethod of making same issuing March 31, 1936 tration, 60 to '75 parts, and solvent naptha or as Patent No. 2,036,130. 7 .other solvent, 25 to 40 parts by weight. The Attempts have been made to utilizelimestone amount of solvent may be varied depending on 40 rock asphalt from Texas deposits in road buildthe maltha content of the rock and upon air 40 ing by adding a soft fluxing material. As the temperature in order tosecure the desired fluidity asphalt contained in such limestone rock is truly of the asphalt cut back. asphaltic pitch and quite hard these attempts As a specific example, to 100 pounds of crushed have not been successful and in reality did not maltha-containing limestone rock graded to utilize the asphalt content of the rock. Other to inch in size and containing 3% of maltha attempts to use limestone rock asphalt containby weight, asphalt cement is added cut back with ing maltha involve heating to a high tempera- 30 to 40% of naptha. The amount of conture in a dryer and these attempts were unsuctained maltha that is com-mingled with the cecessful because the exposure of the maltha or ment is approximately to 1 pounds. Obvimaltha-containing sand or rock to a high temously in order to maintain the ratio of maltha 50 perature is harmfuland destroys the useful propto cement of 1:4 approximately four pounds of erties of adhesiveness and ductility of the natasphalt cement is added, cut back with 1%; to ural maltha. Also where asphaltic cement was 2.7 pounds of solvent. The mixing is carried on added, the proportions of maltha to cement were 7 without heating the materials. approximately in the ratio of 1:1. With this grading or sizing of the rock no other mineral aggregate is desirable or necessary for ordinary purposes as for ordinary pavements or walks. The solvent gradually evaporates leaving the stone coated with a bituminous material consisting of approximately one part of maltha to 3 A; to 5 parts asphaltic cement. This composition is a strong tough asphaltic concrete of ductile and self-healing character adapted to resist traffic impacts. Furthermore the concrete is highly resistant to Water and oxygen and thus produces a paving surface or the like where the concrete is employed that is highly immune chemically against the effects of the seepage of moisture from underneath which seepage is largely responsible for the failure of many bituminous pavements during the last few years.

As an alternative method of making available the natural malthas contained in asphaltic sandstone or limestone, such materials may be crushed to sand size and by the addition of solvent naptha the maltha may be extracted up to practically 100% depending upon the fineness of the sand. Thus to 100 pounds of maltha-containing sand having 3 pounds available maltha are added 12 pounds of asphaltic cement cut back with from 3 to 4% pounds of solvent naptha. Thus 15 pounds of combined maltha and asphaltic cement are obtained. As the 100 pounds of sand require approximately '7 pounds of binder, to this mixture is added approximately 250 pounds of crushed limestone,slag, gravel, or like mineral aggregate. This mix then contains 250 pounds of limestone or mineral aggregate, one hundred pounds of crushed maltha sand rock or lime rock and 12 pounds of asphaltic cement cut back with 3 to 4% pounds of solvent.

In both of the above methods mixing of the ingredients is accomplished by any suitable apparatus such as the rotary mixer, a pug mill or any other mixing method that causes the materials to blend.

It is to be noted that a higher percentage of solvent is specified than is usual in the asphaltic cut back. Sufficient naptha must be provided to liberate the maltha contained in the rock asphalt and may be varied somewhat depending upon the character of the asphalt and weather conditions. A small percentage of moisture in the rock asphalt or crushed rock does not materially afiect the process.

The composition produced by the above described process is particularly advantageous as a paving mixture on account of the ductility and self-healing characteristics of the composition. The essence of the invention consists in extracting partially or substantially entirely the maltha from maltha-impregnated rock or rock sand in a cold state by the addition of asphaltic cement cut back with sufiicient solvent not only to liquefy the cement but also dissolve the maltha from the rock, the proportion of asphaltic cement between three to five times that of the maltha. After evaporation of the naptha or other solvent, the maltha is so combined with the cement as to substantially enhance the durability, adhesiveness and ductility so that the material has desirable properties as a binder for paving compositions and the like.

As indicated above various changes may be made in the detailed processes set forth above as illustrative of the invention and may be made Without departing from the scope of the invention as indicated in the appended claims.

I claim:

1. The method of making paving material which comprises cold-mixing maltha-containing rock material having a maltha content of approximately three per cent by Weight with asphaltic cement made liquid by to 40 parts by weight of solvent, such as naptha, to thereby obtain a ratio of extracted maltha to cement of approximately 1:4.

2. The method of making paving material which comprises cold-mixing approximately one hundred pounds of crushed maltha-containing rock graded to approximately to A inch in size and'having amaltha content of approximately three per cent by weight with approximately four pounds of asphalt cement cut back with 1.33 to 2.7 pounds of solvent, to thereby obtain a ratio of extracted maltha to cement of approximately 1:4.

3. The method of making paving material which comprises cold-mixing maltha-containing sand or finely-divided rock material having a natural maltha content of approximately 3 to 5 with asphaltic cement made liquid by a solvent, such as naptha, in such proportions as will render the mass workable and at the same time extract the maltha from the material in the proportion of approximately one part of maltha to four parts of cement.

JAMES W. FRASER. 

